Children with severe-to-profound sensorineural hearing loss (SNHL) experience significant delays across developmental domains including speech recognition, language, cognition, psychosocial interactions, and academic skills. In an attempt to avert further developmental delays, more than 4,000 American children with severe-to-profound SNHL have undergone cochlear implantation prior to the age of five and rates of implantation are accelerating. Promising clinical studies have generally supported wider application of cochlear implants in children. However, childhood implant research has often involved case-series designs, based in a single center, that evaluated children who used different implant technologies. Further, few studies have examined the impact of cochlear implants on the "whole" child, particularly with longitudinal measures of cognitive, social, and behavioral development. There is also little information available on the perceived benefit of childhood implantation from a perspective of cost- effectiveness. There is a need to establish more powerful predictors of the benefits of childhood cochlear implantation. This need is underscored by the fact that clinical decisions to pursue early cochlear implantation are often prompted by parental choice. Parents of deaf children choose among options that have vastly different implications for the use of medical, (re)habilitative, educational, and other societal resources. A pressing issue concerns the validity of generalizing observed benefits in young children to populations of ever-younger deaf infants. The proposed study will systematically evaluate the predictive value of variables as they relate to outcomes of oral language acquisition, speech recognition skills, selective attention and problem-solving skills, behavioral and social development, parent-child interactions, and quality-of-life measures in children implanted in six U.S. implant centers. Data from this study will contribute to our understanding of the factors predicting implant-associated language use, communication competence in early childhood, psychosocial development, and the perceived value of early cochlear implantation in light of associated costs. Conclusions will enable a refined approach to implant candidacy when considering (re)habilitative strategies designed to optimize the development of children with severe-to-profound SNHL.